Extremely high levels of melanoma in Tauranga, New Zealand: possible causes and comparisons with Australia and the northern hemisphere.

The objective of the study was to determine the incidence of melanoma in the Tauranga region of New Zealand, to compare these findings within Australasia and the northern hemisphere, and to understand the causes of the relatively high rates in Tauranga. Data were obtained from retrospective review of histology reports from the public and private health systems in greater Tauranga (Tauranga and Western Bay of Plenty Districts). Primary cutaneous melanomas (including both invasive and in situ melanomas) reported during 2003 were included. Age-standardized melanoma rates were calculated for the entire population as well as for the non-Maori population of the region, identified from the 2001 New Zealand Census. The age-standardized incidence of invasive melanoma in the non-Maori population of the greater Tauranga region was 79/100,000. The age-standardized rate for the entire population was 70/100,000. The rate of in situ disease was 78/100,000 for non-Maori and 72/100,000 for the entire population. The Tauranga region of New Zealand has an exceptionally high incidence of invasive and in situ melanomas. This is likely related to environmental, geographical and societal factors, including relatively high levels of UV exacerbated in recent times by ozone depletion, relatively cool summer temperatures which encourage outdoor exposure, and relatively fair skin colouring.